Method and system for improving crosstalk attenuation within a plug/jack connection and between nearby plug/jack combinations

ABSTRACT

This application describes a jack for improving crosstalk attenuation. The jack has a housing, a foil at least partially surrounding the housing, a printed circuit board, and at least one pair of insulation displacement contacts and vias. Each pair of insulation contacts and vias are associated with a differential signal. A conductive trace stub is routed on the printed circuit board near the edge of the board proximate to the foil in order to at least partially balance the coupling from one of the insulation displacement contacts and vias of a pair to the foil with the other insulation displacement contact and via of the pair by electrically connecting the trace stub to the via that is further from the foil.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application Ser.No. 61/119,231, filed on Dec. 2, 2008, the entirety of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

There is a continuing need to obtain more margin in communicationchannels for near-end and far-end crosstalk (NEXT and FEXT), and aliennear-end and far-end crosstalk (ANEXT and AFEXT). A major source of NEXTand FEXT occurs within the plug of a plug/jack combination and istypically compensated for within the jack. A major source of aliencrosstalk is common mode noise that couples between channels,particularly between adjacent jacks, and becomes converted intodifferential alien crosstalk (mode conversion).

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are perspective view of an embodiment of a jack with afoil shield according to the present invention;

FIGS. 2A and 2B are perspective view of another embodiment of a jackwith a foil shield according to the present invention;

FIG. 3 is a cross-sectional view taken along section line 3-3 in FIGS.1A and 1B, illustrating a stack-up for the adhesive foil materialaccording to the present invention;

FIG. 4 is a schematic view illustrating alien crosstalk occurring due tocommon mode propagation along jack foil shields in nearby jacks whichconverts back into differential crosstalk in the jack;

FIG. 5 is a fragmentary perspective of an embodiment of a communicationsystem according to the present invention;

FIGS. 6A and 6B are exploded perspective views of an embodiment of amodular jack according to the present invention;

FIGS. 7A and 7B are perspective views of some aspects of the jack ofFIGS. 6A and 6B;

FIG. 8 is a perspective view of the plug interface contacts of the jackof FIGS. 6A and 6B;

FIG. 9 is a see-through perspective view of the multi-layer flex circuitboard of the jack of FIGS. 6A and 6B;

FIG. 10 is a schematic view of the flex circuit board of FIG. 9;

FIG. 11 is a see-through perspective view of the multi-layer rigidcircuit board of the jack of FIGS. 6A and 6B;

FIG. 12 is a schematic view of the rigid circuit board of FIG. 11;

FIG. 13 is a schematic view illustrating how alien crosstalk is reducedaccording to the present invention by blocking common mode propagationalong jack foil shields through the use of a split foil;

FIG. 14 is a perspective exploded view of another embodiment of a jackwith a foil shield according to the present invention, where the foilshield is continuous but the metallization layer has a gap;

FIG. 15 is a perspective exploded view of another embodiment of a jackwith a foil shield according to the present invention, where the foilshield is continuous but the metallization layer is present only on abase and one side;

FIG. 16 is a perspective exploded view of another embodiment of a jackwith a foil shield according to the present invention, where the foilshield is continuous but there are selected areas of the foil which havemetallization layers; and

FIG. 17 is a perspective exploded view of another embodiment of a jackwith a foil shield according to the present invention, where the foilshield is continuous with continuous metallization but the foil onlyincludes a single side and top portions.

Corresponding reference characters indicate corresponding partsthroughout the several views. The examples set out herein illustratesome preferred embodiments of the invention, and such examples are notto be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

Compensation methods and devices are described in a novel design for animproved category 6A (CAT6A) RJ45 jack design, to exceed TIA category 6Astandards at 500 MHz, in U.S. Provisional Patent Application Ser. No.61/090,403, entitled “High-Speed Connector with Multi-StageCompensation,” filed Aug. 20, 2008, which is incorporated by referenceas if fully set forth herein. This jack addresses the need within theindustry to obtain more margin for near end crosstalk (NEXT), far endcrosstalk (FEXT), and return loss in order to meet the needs ofdemanding customers. Additionally, this jack reduces the differential tocommon and common to differential mode conversion (herein referred to as“mode conversion”) that occurs within the jack to improve the aliencrosstalk performance of the system.

U.S. Patent Application Publication No. 2006/0134995, also incorporatedby reference as if fully set forth herein, discloses communicationsjacks which are provided with conductive covering layers to reduce theamount of ANEXT between connectors at insulation displacement contacts(IDCs) when the jacks are installed alongside one another. Theseconductive layers or foils are also part of the above cited U.S.Provisional Patent Application Ser. No. 61/090,403.

In other advances, the present invention addresses some of the currentlimitations in channel and permanent link performance respective to jackreturn loss margin at higher frequencies. In one embodiment of thepresent invention the jack transmission line components can include pluginterface contacts (PICs) that mate with a plug and wrap around a sledand interface with a rigid circuit board, a flex circuit board thatwraps around the sled with components in contact with the PICs, rigidcircuit board circuit elements, and IDCs which also interface with therigid circuit board and which allow for wires within cabling to connectwith the IDCs. The plug/PICs, flex board, PIC region of the rigid board,and a compensation region of the rigid board can be considered a firstimpedance region; and the IDC vias region of the rigid board and IDCscan be considered a second impedance region following the firstimpedance region. If a jack connector has a relatively low impedanceregion (at the first impedance region) followed by a relatively highimpedance region (at the second impedance region) there is more returnloss margin at lower frequencies, but less return loss margin at higherfrequencies. A jack with only the first low impedance region and not arelatively high impedance second region has less margin at lowerfrequencies, but more relative margin (as compared to a jack having alow impedance region followed by a relatively high impedance region) athigher frequencies. This same relationship applies when the magnitudevalues are opposite of that described, such as a jack with a highimpedance region followed by a low impedance region, where an increasein the impedance of the low impedance region improves return loss.

Pair 4-5 is typically the pair with the worst return loss margin athigher frequencies in present day jack designs. Generally speaking, pair4-5 has a low impedance region caused by the plug/PICs, flex board, PICregion of the rigid board, and compensation region of the rigid board,followed by a high impedance region caused by the respective IDCs andwire cap. A feature of the present invention is to reduce the impedanceof the high impedance region so that the return loss gets relativelyworse at lower frequencies, but the margin improves at high frequencies,which results in overall improved return loss margin relative to theCAT6A specification. Since the relationship between impedance andcapacitance generally follows Z=√(L/C), capacitance is added in the highimpedance region to reduce the impedance of the high impedance region.

In a patch panel or outlet where there are many jacks clustered withinan area, high levels of alien crosstalk can occur between theseneighboring jacks. Previous understanding of this concept indicated thatthis coupling was primarily due to inductive differential couplingcaused by the proximity of the neighboring wires and blades in adjacentplugs and jacks, and particularly parallel portions which run adjacentto each other. The foil label designs of FIGS. 1 and 2 address thisproblem. In FIG. 1, jack assembly 20 includes jack 22 and an adhesivelymounted foil label or shield 24. Jack 22 can be a CAT6A jack design, forexample. Alternatively, other jacks such as CAT6, CAT7, or others can beused. FIG. 2 illustrates jack assembly 26 which includes jack 22 and anadhesively mounted foil label 28 with extended sides 29. These foillabels 24, 28 are primarily used to reduce the amount of alien crosstalkoccurring between neighboring jacks, as the level of coupling fromnon-neighboring jacks is already very low due to the fact that they arerelatively far apart. Although not shown in FIGS. 1-2, jacks 20, 26typically can include a wirecap as shown in FIG. 6 and other elements ofFIG. 6. The foil labels include an adhesive material 18 with a metalliner 14, then a paint layer 12 and protective coating 10, which isshown in FIG. 3.

However, it has been observed, that in a channel environment with a highlevel of common mode noise, that the foil shields provide an electricalconnection (comprising a conductive path around the jack with capacitivecoupling to adjacent jacks) for a common mode current to flow to andbeyond neighboring jacks 27 as is shown by the arrows A in FIG. 4. Thisis a significant cause of alien crosstalk between non-neighboring jacks,as well as further increasing the amount of alien crosstalk betweenneighboring jacks. When several jacks, each of which include the foilshields according to FIGS. 1 and 2, are near each other, there exists avery low loss path for a common mode current to travel between jacks duethe large amount of capacitive coupling between neighboring electricallyconductive foils 29, and at least one embodiment of the presentinvention addresses this problem. In the example of FIG. 4, capacitivecouplings 31 occur between neighboring foils 29 due to their closeproximity and large overlapping surface areas. This allows for commonmode transmission with low attenuation for frequencies approximatelybetween 100 and 500 MHz. A common mode current, I, can be formed, asshown by the arrow B. In the illustration of FIG. 4, the spacing betweenthe lacks 27 is enlarged for clarity, and the foils 29 are shown asseparated from the jack housings for illustrative purposes. The commonmode signal in the jacks becomes ANEXT and/or AFEXT.

In another aspect according to the present invention, it is desirable tohave balanced capacitive and inductive loads between all differentialpair combinations within the plug/jack combination in order to minimizemode conversion. It is also desirable to have each differential pairbalanced with respect to the foil label design surrounding parts of thejack in order to further reduce mode conversion.

Herein described is a novel design for a jack with a foil label and animproved rigid circuit board that improves the balance of eachdifferential pair on the jack with respect to the foil label, inaddition to making improvements addressing the problems discussed above.The present invention reduces the mode conversion of the jack andimproves alien crosstalk.

Referring now to the drawings, and more particularly to FIG. 5, there isshown a communication system 30, which can include communication cables,such as patch cables 32 and horizontal cables 33, connected to equipment34. Equipment 34 is illustrated as a patch panel in FIG. 5, but theequipment can be passive equipment or active equipment. Examples ofpassive equipment can be, but are not limited to, modular patch panels,punch-down patch panels, coupler patch panels, wall jacks, etc. Examplesof active equipment can be, but are not limited to, Ethernet switches,routers, servers, physical layer management systems, andpower-over-Ethernet equipment as can be found in datacenters/telecommunications rooms; security devices (cameras and othersensors, etc.) and door access equipment; and telephones, computers, faxmachines, printers and other peripherals as can be found in workstationareas. Communication system 30 can further include cabinets, racks,cable management and overhead routing systems, and other such equipment.

Communication cables 32 and 33 are shown in the form of an unshieldedtwisted pair (UTP) cable, and more particularly a CAT6A cable which canoperate at 10 Gb/s. However, the present invention can be applied toand/or implemented in connection with a variety of communicationscables. Cables 33 can be terminated directly into equipment 34, oralternatively, can be terminated in a variety of punchdown or jackmodules 40 such as RJ45 type, jack module cassettes, and many otherconnector types, or combinations thereof. Patch cables 32 are typicallyterminated in plugs 36.

FIG. 6 shows a more detailed exploded view of jack 40 which generallyincludes housing 42 that fits an RJ45 plug, a nose 44 that has eightPICs 56 that mate with a plug and wrap around sled 60, and interfacewith a rigid board 46. Rigid board 46 connects to IDCs 48, and rear sled50 that holds the IDCs. A wire cap 52 allows for wires within cabling toconnect with the IDCs, and this is also part of the jacks of FIGS. 1-2,although not shown in the views. Nose 44 includes a flex circuit board54, plug interface contacts 56, front bottom sled 58 and front top sled60. FIGS. 1 and 2 are different from FIG. 6 in that they respectivelyshow the two foil label designs 24, 28, whereas FIG. 6 illustrates animproved foil label 70 (see also FIG. 7) having a first side 72 and amirror image second side 74, with a gap 76 therebetween. The design ofrigid board 46 described herein works with all three of these foils 24,28 and 70. Like foil 28, foil label 70 includes extensions 78 that helpreduce coupling between plugs and PICs in adjacent jacks.

Crosstalk compensation components can be included on both PICS 56 andflexible board 54, as shown in FIG. 8 and FIGS. 9-10, respectively. FIG.8 shows the PICs 56 in order from the first through the eighth contacts.Areas shown in FIG. 8 include: (a) an area 81 that creates capacitiveand inductive coupling between the conductors 4 and 6 in the nose(compensation between pair 4-5 and pair 3-6); (b) an area 83 thatcreates capacitive and inductive coupling between conductors 6 and 8 inthe nose (compensation between pair 3-6 and pair 7-8); (c) an area 85that creates capacitive coupling between conductors 3 and 5 in the nose(compensation between pair 4-5 and pair 3-6); and (d) an area 87 thatcreates capacitive and inductive coupling between conductors 1 and 3 inthe nose (compensation between pair 3-6 and pair 1-2). An area 89 of thenose that interfaces with the plug is removed for clarity. In FIG. 9,the flex board 54 with its capacitors is shown. The portion of the flexboard that makes contact with the PICs at the nose is shown at 91, andthe contact areas 1″-8″ make contact with plug interface contacts 1-8 asshown in FIG. 8. Referring particularly to FIGS. 11 and 12, rigid board46 also includes crosstalk compensation components (either the same oropposite of polarity of plug crosstalk components), which are identifiedparticularly in FIG. 12, with the exception of C45. C45 improves returnloss margin at higher frequencies in pair 4-5 by reducing the relativelyhigh impedance of the second impedance region, as previously discussed.Although the return loss gets relatively worse at lower frequencies as aresult of this modification, the overall margin improves over thefrequency band of interest. Rigid board 46 includes lattice typecompensation as also discussed in U.S. Provisional Patent ApplicationSer. No. 61/090,403.

One of the novel aspects of the present invention is that it addresses anaturally unbalanced coupling which exists between all pairs and thefoil label on the jack. The primary reason for this unbalance is shownin FIG. 6. The IDCs 48 that are near the edge of the jack (pins 5, 2, 6,7) capacitively couple more strongly to the foil than the IDCs 48 (pins4, 1, 3, 8) not near the edge of the jack. This is especially true onpair 4-5 and pair 1-2 where IDCs 5 and 2 are near the foil, and 1 and 4are far away from it.

An embodiment of a rigid board solution for balancing the pairs withrespect to the foil shield is shown in FIG. 11. FIG. 11 shows thelocation of foil covering 70 at D (labeled D(70) in the figure). In thisembodiment rigid board 46 has four layers of conductive traces. The IDCvias receive and retain IDCs. The IDC vias are numbered 5′-4′-1′-2′ atthe top of the board in FIGS. 11, and 7′-8′-3′-6′ on the bottom edge ofthe board, and are also plated through holes which interconnect some ofthe traces on the various layers. Signals or noise can couple relativelystrongly to foil label 70, particularly through the IDC vias and IDCs5′, 2′, 6′, and 7′. For pair 4-5, for example, IDC via 5′ and IDC 5′ aremuch closer to the foil label 70 than IDC via 4′ and IDC 4′ are. Tobalance this pair, conductive trace stub 90 is routed close to the edgeof board 46 near the foil 70 and is electrically connected to trace 4 (aconductive trace interconnecting PIC via 4 with IDC via 4′) by itsconnection to PIC via 4. Stub 90 thereby balances conductor 4 withrespect to conductor 5 and the foil. Additionally and/or alternatively,trace 4 can be routed relatively close to the edge of rigid board 46 toincrease the coupling to foil 70. In the embodiment shown stub 90 is0.008 inches wide by 0.220 inches long in one half ounce copper(approximately 0.0007 inches thick), although other thicknesses, widthsand lengths are possible. FIG. 11 shows at 1-8 the vias where thecorresponding plug interface contacts are attached to the rigid board48.

Similarly for pair 1-2, for example, IDC via 2′ and IDC 2′ are muchcloser to foil 70 than IDC via 1′ and IDC 1′ are. To balance this pair,conductive trace stub 92 is routed close to the edge of board 46 nearthe foil 70 and connected to trace 1 (conductive trace interconnectingPIC via 1 with IDC vial') via plated through hole 94. Stub 92 is similarto stub 90; however, because of space limitations on rigid board 46,stub 92 is only 0.005 inches wide by 0.075 inches long, also in oneounce copper (approximately 0.0014 inches thick plus additional platingto achieve a thickness between 0.002-0.0035), although otherthicknesses, widths and lengths are possible. To compensate for thisrelatively short length the pair 1-2 is further balanced by moving trace1 very close to the board edge (closer to foil 70), and plated throughhole 94 provides significant surface area in a third dimension (boardthickness) which also capacitively couples to foil 70, giving strongercoupling between conductor 1 and the foil 70, thereby balancing the pair1-2 with respect to foil 70. Unplated through holes generally at 96reduce capacitance between traces 4 and 5 closer to the area of NEXTcompensation to lessen the effects of compensation elements on returnloss, by better impedance matching.

The result of the pair balancing with respect to the foil, and the useof a split foil is illustrated in FIG. 13. Capacitive couplings 101between neighboring foils 72 and 74 are significantly attenuated by thegaps 76. The present invention achieves less common mode current I′ inthe direction of arrow C on the foil due to pair balancing relative tothe foil, and the split foil eliminates the low-loss path forpropagation of the common mode current from adjacent jack to adjacentjack. The overall improvement in alien crosstalk margin has been shownto be at least 4 dB with the improvements of the present invention.Further, the present invention can be used advantageously with each ofthe symmetric foil designs of FIGS. 1, 2, 6 and 14, although the designsof FIGS. 1 and 2 would not have the characteristics and advantages ofthe split shield. FIG. 14 includes a continuous single piece foil 103with a gap 105 in the metallization.

In other aspects of the present invention, through hole 100 (shown inFIG. 11) is meant to have the opposite effect as C45, and through hole98 can be eliminated as unnecessary. The addition of capacitor C24 andelimination of C15 improves NEXT on pair combination 45-12, relative tothe invention of U.S. Provisional Patent Application Ser. No.61/090,403. Some other comparisons to U.S. Provisional PatentApplication Ser. No. 61/090,403 are as follows. Using inductive traceL3, along with the new inductor L3L, connects trace 3 to C38 and usesthe lattice compensation and improves 36-78 NEXT. Changing theorientation of L6 to move it further away from the side of the rigidboard reduces coupling to the foil. Moving the location of C58 and C16better accommodates the new artwork of the present invention.

The asymmetric foil designs of FIGS. 15-17 typically requiremodifications to the balance circuitry shown in FIG. 11, such as smallerbalance components on the side of rigid board 46 which have less, or no,conductive shielding. That is, smaller balance components are beingprovided on a particular portion of the rigid board that does not lieadjacent any conductive foil or shielding. Conceptually, eachdifferential pair needs to achieve balance with each part of the foil somultiple foil parts require each foil part to be balanced with respectto the jack. FIG. 15 illustrates an embodiment of the foil label 107where one side 109 does not have any metal (note that the embodimentshown here could be flipped so the opposite side is metalized) In theembodiment of the FIG. 15, the side 109 without metal may consist ofadhesive, paint, and protective layers only, while the other side 111 isprovided with a metal liner. FIG. 16 illustrates an embodiment of thefoil label 113 with areas 115 selectively chosen for metallization; andFIG. 17 illustrates an embodiment of the foil label 117 which is anL-shaped metalized foil where one side of the jack and the top or baseare covered by the foil leaving one side without any covering. Note thatthe embodiment shown in FIG. 17 can be modified by making the oppositeside with a foil and the side shown in FIG. 17 removed.

Alternative embodiments of the present invention include a jack with thecircuit board of FIG. 11, but with a capacitor C15 between IDC vias 1and 5, or a jack with the circuit board of FIG. 11, but with capacitorC24 completely removed from the board along with any traces connected toit. Another alternative embodiment of the present invention eliminatesthe flex board.

While this invention has been described as having a preferred design,the present invention can be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles.

1. A jack for improving crosstalk attenuation, comprising: a housing; a foil at least partially enclosing the housing; a printed circuit board; first and second insulation displacement contacts, the first insulation displacement contact being located closer to the foil than the second insulation displacement contact, the first and second insulation displacement contacts being associated with a first differential signal; and a first conductive trace stub electrically connected to the second insulation displacement contact routed proximate to an edge of the printed circuit board and proximate to the foil, the first conductive trace stub configured to at least partially balance coupling from the first insulation displacement contact to the foil with coupling from the second insulation displacement contact to the foil for the first differential signal.
 2. The jack for improving crosstalk attenuation of claim 1, further comprising a first via associated with the first insulation displacement contact and a second via associated with the second insulation displacement contact, the first conductive stub also configured to at least partially balance coupling from the first via to the foil with coupling from the second via to the foil for the first differential signal.
 3. The jack for improving crosstalk attenuation of claim 2, further comprising a sled.
 4. The jack for improving crosstalk attenuation of claim 3, further comprising a wire cap.
 5. The jack for improving crosstalk attenuation of claim 4, further comprising plug interface contacts.
 6. The jack for improving crosstalk attenuation of claim 1, further comprising signal traces on the printed circuit board associated with the first differential signal, a portion of the traces being located close to an edge of the printed circuit board and proximate to the foil in order to aid in balancing coupling from the first insulation displacement contact to the foil with coupling from the second insulation contact to the foil for the first differential signal.
 7. The jack for improving crosstalk attenuation of claim 2, further comprising signal traces on the printed circuit board associated with the first differential signal, a portion of the traces being located close to an edge of the printed circuit board proximate to the foil in order to aid in balancing coupling from the first insulation displacement contact and first via to the foil with coupling from the second insulation and second via contact to the foil for the first differential signal.
 8. The jack for improving crosstalk attenuation of claim 1, further comprising: third and fourth insulation displacement contacts, the third and fourth insulation displacement contacts being associated with a second differential signal, the third insulation displacement contact being closer to the foil than the fourth displacement insulation contact; and a second conductive trace stub, the second conductive stub being routed proximate to an edge of the printed circuit board and proximate to the foil, and further configured to at least partially balance the coupling from the third insulation displacement contact to the foil with the coupling from the fourth insulation displacement contact to the foil for the second differential signal.
 9. The jack for improving crosstalk attenuation of claim 8, further comprising a third via associated with the third insulation displacement contact and a fourth via associated with the fourth insulation displacement contact, the conductive stub also configured to at least partially balance the coupling from the third via to the foil with the coupling from the fourth via to the foil for the second differential signal.
 10. The jack for improving crosstalk attenuation of claim 8, further comprising a sled.
 11. The jack for improving crosstalk attenuation of claim 10, further comprising a wire cap.
 12. The jack for improving crosstalk attenuation of claim 11, further comprising plug interface contacts.
 13. The jack for improving crosstalk attenuation of claim 8, further comprising signal traces on the printed circuit board associated with the second differential signal, a portion of the traces being located close to an edge of the printed circuit board proximate to the foil in order to aid in balancing coupling from the third insulation contact to the foil with coupling from the fourth insulation contact and the foil.
 14. The jack for improving crosstalk attenuation of claim 9, further comprising signal traces on the printed circuit board associated with the second differential signal pair, a portion of the traces being located close to an edge of the printed circuit board proximate to the foil in order to aid in balancing coupling from the third insulation contact and third via to the foil with coupling from the fourth insulation contact and fourth via to the foil. 